Hello all,

I recently purchased a broken 54520A hoping to be able to repair it.
The seller said that the screen was faulty. However, after the
oscilloscope arrived, I saw very soon that the problem was not the
screen but something else.

When the oscilloscope boots, the fan turns on and all the indicators
on the front pannel light-on. But it hangs there. No keyboard response
and nothing displayed on the screen. However, the screen is working,
as when I turn off the device, sometimes I can see the beam on the
display and some noise.

The indicators keep lighted on until you turn the oscilloscope off
again.

Could anybody help me? Its a great oscilloscope, but it just does
not work :-(

Juan

wrote:
Hello all,

I recently purchased a broken 54520A hoping to be able to repair it.
The seller said that the screen was faulty. However, after the
oscilloscope arrived, I saw very soon that the problem was not the
screen but something else.

When the oscilloscope boots, the fan turns on and all the indicators
on the front pannel light-on. But it hangs there. No keyboard response
and nothing displayed on the screen. However, the screen is working,
as when I turn off the device, sometimes I can see the beam on the
display and some noise.

The indicators keep lighted on until you turn the oscilloscope off
again.

Could anybody help me? Its a great oscilloscope, but it just does
not work :-(

Juan



I assume this is a DSO? Start with the simple stuff, check the power
supply voltages, see if the CPU clock is running, have a look at the
reset line, that should provide some insight.

Yes, its an HP 54520A digitizing oscilloscope.

I will check if all the voltages are OK. According to the service
manual I have to search around for a 2 Ohms 25 Watt resistor to load
the power supply.

I will post my results here.

Juan

On 17 abr, 00:38, James Sweet wrote:
wrote:
Hello all,

I recently purchased a broken54520Ahoping to be able to repair it.
The seller said that the screen was faulty. However, after the
oscilloscope arrived, I saw very soon that the problem was not the
screen but something else.

When the oscilloscope boots, the fan turns on and all the indicators
on the front pannel light-on. But it hangs there. No keyboard response
and nothing displayed on the screen. However, the screen is working,
as when I turn off the device, sometimes I can see the beam on the
display and some noise.

The indicators keep lighted on until you turn the oscilloscope off
again.

Could anybody help me? Its a great oscilloscope, but it just does
not work :-(

Juan

I assume this is a DSO? Start with the simple stuff, check the power
supply voltages, see if the CPU clock is running, have a look at the
reset line, that should provide some insight.- Ocultar texto de la cita -

- Mostrar texto de la cita -

wrote:

Hello all,

I recently purchased a broken 54520A hoping to be able to repair it.
The seller said that the screen was faulty. However, after the
oscilloscope arrived, I saw very soon that the problem was not the
screen but something else.

When the oscilloscope boots, the fan turns on and all the indicators
on the front pannel light-on. But it hangs there. No keyboard response
and nothing displayed on the screen. However, the screen is working,
as when I turn off the device, sometimes I can see the beam on the
display and some noise.

The indicators keep lighted on until you turn the oscilloscope off
again.

Could anybody help me? Its a great oscilloscope, but it just does
not work :-(

Juan

Here are aso some experts to find:

http://tech.groups.yahoo.com/group/h...ent_equipment/

Jorgen
dj0ud

Juan,

There may be a lithium cell which is used to maintain the static ram
where calibration data is stored. In the 5454x series of 'scopes the
system locks up exactly as you describe when the lithium cell is
discharged. This seems to happen about 15 years after manufacture.

The service manual makes no mention of this problem!

I had a similar problem with my HP 54542A 'scope and another poster
had this problem with his HP 54540.

Replacing the lithium cell and running the self-calibration fixed the
problem for both of us.

For more information, search this group (sci.electronics.repair) for
"54540A".

John